Recently, as the display technology develops increasingly, high performance display apparatuses have been more and more used in various public places such as plazas, stations, service windows and railway transportation carriages. In particular, for a railway transportation carriage, several display terminals are usually installed within the carriages. In order to ensure passengers in the same carriage or between different carriages can watch the display pictures synchronously, it is necessary to make the display signals of respective display terminals highly synchronous.
With the fast development of the city railway transportation, the demand for railway transportation vehicles is also increasing continuously, and the vehicle workers have higher and higher demands on simplification of the site operation. In the existing railway transportation, the transmission scheme for audio and video signals of the display terminals within the carriages is usually that one carriage has one signal controller, and such a signal controller encodes multiple paths of differential signals to be output and is connected to each display terminal simultaneously by network cables in order to achieve the object that the signal controller transmits signals to each display terminal simultaneously. As shown in FIG. 1, taking that one carriage is provided with one signal controller and 4 display terminals as an example, the signal controller 11 is connected to four display terminals respectively by network cables. In the practical application procedure, the cable length of the network cable between the signal controller 11 and the display terminal 121 is usually 20 m. If the display terminals are uniformly arranged and separated by 10 m between every two adjacent display terminals, the cable length of the network cables between the signal controller 11 and the display terminal 122 is 30 m, and the others can be obtained similarly. It can be seen that the total cable length for connecting the signal controller and the display terminals are around 140 m when there are four display terminals. In addition, the adoption of such a synchronous display scheme involves a problem of bending when several network cables are wired simultaneously during the installation, and thus the network cable wiring is very cumbersome. Moreover, with the increasing of the distance between the display terminals and the signal controller, the audio and video logical cable length increases dramatically, and this further increases the cost of the network cable placement.